Method and apparatus for determining deterioration of secondary battery, and power supply system therewith

ABSTRACT

A method for detecting SOC and SOH of a storage battery includes: calculating an SOC value of the storage battery with use of an SOC calculation unit based on a measured voltage value or a measured current value of the storage battery and calculating an SOH value of the storage battery with use of an SOH calculation unit based on the SOC value; further calculating a new SOC value with use of the SOC calculation unit based on the SOH value and calculating a new SOH value with use of the SOH calculation unit based on the new SOC value, these further calculations of SOC value and SOH value being repeated a prescribed n times of at least one so as to obtain an nth calculated SOC value and an nth calculated SOH value; outputting the nth calculated SOH value as an SOH output value and outputting the nth calculated SOH value as an SOC output value; and storing the SOH output value into a memory.

TECHNICAL FIELD

The present invention relates to a method for determining a state ofhealth (SOH) of a secondary battery supplying power to a load. Moreparticularly, the present invention relates to a method for determiningthe SOH of a secondary battery based on an estimation result of aninternal impedance or an internal resistance of the secondary battery.

BACKGROUND ART

As a method for detecting a state of charge (SOC) of a storage battery,for example, as described in Japanese Unexamined Patent ApplicationPublication No, 2004-530880, there is a method for estimating SOC bymeasuring the battery voltage with using the relation (linearity)between a battery voltage and SOC.

In this method, it is not possible to measure a stabilized batteryvoltage because the battery voltage is greatly affected by theover-voltage due to charge or discharge. Particularly, in the vehicle,the storage battery supplies a power to each load during and afterengine start and is charged by a charger as well, thereby being chargedand discharged repeatedly. Accordingly, the stabilized battery voltagecan not be obtained, resulting in generation of significant errors inestimation of the SOC obtained from the linearity.

Therefore, for a storage battery mounted on the vehicle, particularly, astorage battery supplying a power to a load only at emergency withoutregularly being connected to the load, there is a method for estimatingSOC by substituting a measured data of battery voltage into a linearexpression after measuring the battery voltage during the period betweenan door-open and engine startup, or a method for estimating SOC byperiodically detecting battery voltages for long hours with a timer toobtain stabilized voltage values. The methods described above are lackof accuracy, because the methods utilize the measured raw data for theestimation and there is no consideration of, for example, a state ofhealth (SOH).

Besides, methods for estimating an SOC of a storage battery during beingcharged includes a method in which a charged amount is calculated bymultiplying the current value by hour, followed by comparing the chargedamount with battery capacity and normalizing data.

However, the battery capacity of the storage battery is lowered anddecreased from its initial capacity in accordance with the deteriorationof the storage battery, thus the accuracy of the calculated SOC becomeslower than that of the initial stage associated with the deterioration.Specially, this tendency appears outstandingly in the case when an SOCis low due to, for example, the discharge of the battery. As measuresagainst this problem, there has been known methods for correcting abattery capacity based on the deterioration level as described inJapanese Patent Application Publications No. H6-59003 and No.2000-166109.

The methods for correcting a battery capacity based on a deteriorationlevel described in Japanese Patent Application Publications No. H6-59003and No. 2000-166109 include: estimating a residual charge at the fullcharged (SOC: 100%) based on the residual charge at heavy loadedobtained by using the IV method which calculates the relation betweenthe discharge current of the storage battery and the battery voltage atevery SOC; calculating a deterioration level by dividing the residualcharge by the battery capacity; and correcting the battery capacity inaccordance with the deterioration level.

These methods also use only the SOC at the time when measured todetermine an SOC and thus lack the accuracy of the determination.

There are methods for detecting an SOH such as a method for detecting anSOH based on an increase of an internal resistance of a battery, amethod for detecting an SOH from a voltage when a storage battery isdischarged, and a method for detecting an SOH by estimating a capacityof a storage battery from a voltage when the battery is discharged. Anyof the methods use only an SOH at the time when measured withoutconsideration of factors, like temperature or other and thus lack theaccuracy of the determination of an SOH.

Technology for determining an SOH of a secondary battery such as a leadbattery mounted on the vehicle and the like is described in JapanesePatent Application Publication No. 2001-228226.

Generally, since there is a strong correlation between an internalimpedance or an internal resistance and an SOH of a secondary battery,if an internal impedance or an internal resistance of a secondarybattery can be obtained, it is possible to determine a deteriorationlevel of the secondary battery from the obtained result. This makes itpossible to inform the user of the need for replacing the deterioratedbattery.

In order to determine an SOH of the secondary battery in a power supplysystem having a secondary battery, it may be employed a construction inwhich the secondary battery is charged or discharged with a specifiedcurrent, a current and a voltage at that time are measured, and aninternal impedance or an internal resistance is calculated from themeasured current and voltage by using a specified operation.

In the case when a secondary battery is mounted on the vehicle and thelike, it is important that normal operation of the secondary battery beguaranteed over a very wide range of operating temperature in supposingthe usage in various areas and environments.

Meanwhile, the internal impedance or internal resistance of thesecondary battery has a tendency to be changed a great deal depending ontemperature and to be significantly increased specially at lowtemperature. Accordingly, even if the internal impedance or internalresistance falls within the allowable range at normal temperature, theymay be out of the allowable range at lower temperature, and thus it maynot be able to use the secondary battery under the lower temperature.

Consequently, it becomes important to accurately determine the SOHregardless of the operating temperature of the second battery, thus itis required that the internal impedance or internal resistance should beestimated after temperature correction by means of any method. Theinternal impedance or internal resistance of the secondary battery has acomplicated temperature characteristic, so it is difficult to make anaccurate approximation with a simple approximate formula, and it hasbeen difficult to make temperature correction for the internal impedanceor internal resistance with high accuracy.

Japanese Patent Application Publication No. 2005-091217 discloses therelated technology for determining SOH of a secondary battery with highaccuracy by correcting a temperature characteristic of an internalimpedance with use of a polynomial expression of at least the third ormore degree.

Generally, the impedance of the battery has a strong correlation withthe deterioration level or discharge capability of the battery, thus, ifthe impedance of the battery can be obtained, the deterioration level ordischarge capability of the battery can be estimated by the obtainedimpedance. This makes it possible to inform the user of the need forreplacing the deteriorated battery or the battery having lowereddischarge capability.

In order to estimate a deterioration level or discharge capability of asecondary battery in a power supply system having the secondary battery,there has been conventionally known a method which includes: letting aspecified charge current or discharge current flow to the battery;measuring the current and the voltage at the time; and calculating theinternal impedance by a specified operation from the measured currentand voltage.

The impedance of the battery can be an index for showing an accuratedeterioration level or discharge capability of the battery ifmeasurements are carried out under the same conditions. However, in thecase where the impedance measurement is applied to a practical system,specially to the vehicle as a typical example, a charge current and adischarge current such as a charge current regularly flowing from analternator to the battery and a discharge current to be supplied to eachelectric device flow through the battery mounted on the vehicle during anormal operation.

Thus, the impedance measurement has been performed in the state that thecharge current and the discharge current during the normal operation aresuperimposed with or added to the specified charge current or thedischarge current described above, without considering the difference ofthe measuring condition due to the superimposed charge/dischargecurrent.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

Charge capability and discharge capability of the storage battery varydepending largely on conditions and states thereof. The conditions andstates include variation of SOC and deterioration of the storagebattery. The charge amount in the storage battery, which is the basisfor calculating the SOC, varies in accordance with the temperaturechange of the environments and the condition and state of charging ordischarging.

Since the SOC is regularly prescribed by the discharge capability andthe discharge characteristics during the time when a long-hour dischargeis performed, the deterioration of the storage battery inevitablyaffects the calculation of the SOC. On the other hand, when calculatingthe SOH, depending on the definition thereof, the SOH calculation is nota little affected by an SOC. Accordingly, the SOC and the SOH have beencorrected in some way. The conventional detection methods includes, forexample, a method in which the correction is made based on thedeterioration level when calculating the SOC, and a method in which thecorrection is made based on an SOC when calculating an SOH. That is,conditioning factor for correcting the SOC and SOH is independentlyconsidered in each detection method. Thus, the difference inaccuracybetween the SOH detection and the SOC detection may be caused, making itdifficult to optimally manage the storage battery.

The above-described conventional methods for determining a deteriorationof a secondary battery have problems as described hereinafter. A currentand a voltage are measured at the time when the secondary battery ischarged or discharged with a specified current to calculate an internalimpedance. In the case where the specified current is a low frequency AC(Alternative Current) of 20 Hz or less, the method according to theJapanese Patent Application Publication No. 2005-091217 can determinethe deterioration of the secondary battery.

However, there has been a problem that noise is not negligible in thecase where the specified current is the low frequency AC of 20 Hz orless. In other words, since an alternator may be used to charge thesecondary battery with the specified current, the noise from thealternator is not negligible in the case of the low frequency AC of 20Hz or less. Further, the noise from a load affects the measurement whenthe specified current is discharged.

Accordingly, it is required that the AC of 100 Hz or higher frequency isused as the specified current, so as to prevent the influence of thenoise from the alternator or the load. Besides, in the case where apulse DC (Direct Current) is used for the specified current, it isnecessary to use the current value and voltage value measured within 10ms of starting the pulse current input for the calculation of theinternal impedance thereof.

However, in the case where the AC of 100 Hz or higher frequency or theresponse within 10 ms of starting the pulse current input is used as thespecified current, the method for determining a deterioration of asecondary battery described in Japanese Patent Application PublicationNo. 2005-091217 has been not able to determine a deterioration of asecondary battery with sufficient accuracy.

Furthermore, the above-described conventional method for estimating adeterioration level or a discharge capability of a secondary battery hasa problem as follows. Specifically, there has been known that theimpedance of the battery depends on magnitude each of a charge currentand a discharge current in the normal operation described above, and itis difficult to estimate an accurate deterioration and dischargecapability under such environment.

One object of the present invention is to provide a method and apparatusfor detecting SOC and SOH of a storage battery capable of performing anoptimum management by detecting both the SOC and the SOH accurately atthe same level. Another object of the present invention is to provide amethod for determining SOH of a secondary battery capable of determiningthe SOH of the secondary battery with high accuracy by accuratelycorrecting a change of internal impedance or internal resistance due tothe operating temperature of the secondary battery. Still another objectof the present invention is to provide a method for estimating adeterioration level or a discharge capability of a battery, byestimating am impedance at a reference direct current value, with theinfluence of the impedance due to a charge current and a dischargecurrent that is superimposed in normal operation being eliminated.

Means for Solving the Problems

A first aspect of the present invention to resolve the problems is amethod for detecting SOC and SOH of a storage battery which includes:calculating an SOC value of the storage battery with use of an SOCcalculation unit based on a measured voltage value or a measured currentvalue of the storage battery and calculating an SOH value of the storagebattery with use of an SOH calculation unit based on the SOC value;

further calculating a new SOC value with use of the SOC calculation unitbased on the SOH value and calculating a new SOH value with use of theSOH calculation unit based on the new SOC value, these furthercalculations of SOC value and SOH value being repeated a prescribed ntimes of at least one so as to obtain an nth calculated SOC value and annth calculated SOH value;

outputting the nth calculated SOH value as an SOH output value andoutputting the nth calculated SOC value as an SOC output value; and

storing the SOH output value into a memory.

A second aspect of the present invention is a method of the firstaspect, in which the SOC output value is also stored in the memory.

A third aspect of the present invention is a method of the first orsecond aspect, in which the SOC calculation is repeated until the newSOH value converges to a specified range.

A fourth aspect of the present invention is a method of any one of thefirst to third aspects, in which a first calculated SOC value firstlyobtained with use of the SOC calculation unit is obtained by correctingthe measured voltage value or the measured current value based on eitherone of an initial SOH value set in advance and a previous SOH outputvalue lastly stored in the memory.

A fifth aspect of the present invention is a method of any one of thefirst to third aspects, in which the SOH calculation unit calculates theSOH value by correcting a measured internal impedance value of thestorage battery based on the SOC value.

A sixth aspect of the present invention is a method of the fifth aspect,in which the measured internal impedance value at a measurementtemperature of the storage battery is corrected to a internal impedancevalue at a specified temperature.

A seventh aspect of the present invention is a method of any one of thefirst to sixth aspects, in which the SOC calculation unit calculates theSOC value by substituting one of: a measured value of an open-circuitvoltage (OCV) of the storage battery; and a corrected value obtained bycorrecting the measured value of the OCV based on an initial SOH valueor a newest SOH value, into a functional expression.

A eighth aspect of the present invention is a method of any one of thefirst to fifth aspects, in which the SOC calculation unit calculates achange in the SOC value based on a discharge current or a charge currentof the storage battery, corrects the change in the SOC value inaccordance with SOH value, and adds the corrected change in the SOCvalue to the SOC value obtained in the previous calculation so as tocalculate the new SOC value.

A ninth aspect of the present invention is a method of any one of thefirst to eighth aspects, in which, when the SOH output values in thememory three times or more are stored, a slope of the change of the SOHoutput values with respect to a number of the storing is determined, and

if the last stored SOH output value falls within an allowable range, thelast stored SOH output value stored in the memory is decided as a truevalue, while if the last stored SOH output value is out of the allowablerange, the last stored SOH output value is deleted from the memory, andthen, a new SOC output value and a new SOH output value are determinedthrough the measurement and/or calculation.

A tenth aspect of the present invention is a method of any one of thefirst to eighth aspects, in which, when the SOH output values in thememory three times or more are stored, a slope of the change of the SOHoutput values with respect to a number of the storing is determined, and

if the last stored SOH output value is out of the allowable range, analert is issued.

A eleventh aspect of the present invention is an apparatus for detectingSOC and SOH of a storage battery which includes: an SOC calculation unitconfigured to: execute a first calculation of an SOC value of thestorage battery based on a measured voltage value or a measured currentvalue of the storage battery; execute a second calculation of an SOCvalue by correcting the measured voltage value or the measured currentvalue of the storage battery in accordance with an SOH value of thestorage battery; repeat the second calculation a prescribed n times ofat least two; and output an nth calculated SOC value as an SOC outputvalue;

an SOH calculation unit configured to: repeatedly calculate an SOH valueof the storage battery based on the calculated SOC value the prescribedn times corresponding to a repeat number of the SOC calculation; andoutput an nth calculated SOH value as an SOH output value; and

a memory for storing at least a plurality of the SOH output values amongthe SOH and SOC output values, respectively obtained in the nthcalculation.

A twelfth aspect of the present invention is an apparatus of theeleventh aspect, which further includes a control unit configured to:determine a slope of a change of the SOH output values with respect to anumber of the storing times in the memory when the SOH output value isstored in the memory three times or more; decide a newest SOH outputvalue as a true value if the newest stored SOH output value of thestored values falls within an allowable range; and delete the newest SOHoutput value and obtain again an SOC output value and an SOH outputvalue through the measurement and/or the calculation if the newest SOHoutput value is out of the allowable range.

A thirteenth aspect of the present invention is a method for determiningSOH of a secondary battery according to an internal impedance or aninternal resistance of the secondary battery supplying power to a load,which includes: preparing in advance a specified temperaturecharacteristic function which contains at least one exponential termsand one adjustment parameter and expresses a temperature dependency ofthe internal impedance or the internal resistance; calculating theinternal impedance or the internal resistance based on a measuredcurrent value or a measured voltage value at the time when the secondarybattery is charged or discharged with a specified current; determining avalue of the adjustment parameter by substituting the measuredtemperature at the time when the secondary battery is charged ordischarged with the specified current and the calculated internalimpedance or the internal resistance to the temperature characteristicfunction; calculating a reference internal impedance or a referenceinternal resistance by substituting the determined adjustment parametervalue and a specified reference temperature into the temperaturecharacteristic function; and determining the SOH of the secondarybattery based on the calculated reference internal impedance or thecalculated reference internal resistance.

A fourteenth aspect of the present invention is a method for determiningan SOH of a storage battery in which the temperature characteristicfunction is expressed by:Z(Temp) or R(Temp)=f(C)×exp{g(C)/Temp}+Cwhere Z is the internal impedance, R is the internal resistance, C isthe adjustment parameter, and f and g express a specified functionrespectively.

A fifteen aspect of the present invention is a method of the thirteenthor fourteenth aspect, which further includes: setting in advance a firstthreshold for determining the SOH based on the reference internalimpedance and a second threshold for determining the SOH based on thereference internal resistance, respectively; comparing the referenceinternal impedance with the first threshold when the reference internalimpedance was calculated, and comparing the reference internalresistance with the second threshold when the reference internalresistance was calculated; and determining the SOH of the secondarybattery based on either of two comparison results.

A sixteenth aspect of the present invention is a method of any one ofthe thirteenth to fifteenth aspect, in which the internal impedance iscalculated based on the measured current value and the measured voltagevalue at the time when the secondary battery is charged or discharged atan AC of 100 Hz or more frequency as the specified current.

A seventeenth aspect of the present invention is a method of any one ofthe thirteenth to fifteenth aspects, in which the secondary battery ischarged or discharged with a pulse current as the specified current, andthe internal resistance is calculated based on measured values of thecurrent and voltage measured within 10 ms of starting the charge ordischarge.

A eighteenth aspect of the present invention is an apparatus fordetermining an SOH of a secondary battery based on an internal impedanceor an internal resistance of the secondary battery supplying power to aload, which includes: a charging circuit for charging the secondarybattery with a specified current; a discharging circuit for dischargingthe secondary battery with a specified current; a current sensor formeasuring a current of the secondary battery; a voltage sensor formeasuring a voltage of the secondary battery; a temperature sensor formeasuring a temperature of the secondary battery; and a control unit for(i) receiving a measured current value, a measured voltage value, and ameasured temperature value from the current sensor, the voltage sensor,and the temperature sensor, respectively, at the time when the secondarybattery is charged or discharged with the specified current by thecharging circuit or the discharging circuit, (ii) calculating theinternal impedance or the internal resistance based on the measuredcurrent value and the measured voltage value, (iii) determining a valueof a adjustment parameter by substituting the calculated internalimpedance or the calculated internal resistance and the measuredtemperature into a temperature characteristic function which contains atleast one exponential terms and one adjustment parameter and expresses atemperature dependency of the internal impedance or the internalresistance, (iv) calculating a reference internal impedance or areference internal resistance by substituting the decided adjustmentparameter value and a specified reference temperature into thetemperature characteristic function, and (v) determining an SOH of thesecondary battery based on the calculated reference internal impedanceor the calculated reference internal resistance.

A nineteenth aspect of the present invention is an apparatus of theeighteenth aspect, which further includes: a storage unit storing inadvance a first threshold for determining deterioration based on thereference internal impedance, and a second threshold for determiningdeterioration based on the reference internal resistance, wherein thecontrol unit compares the reference internal impedance and the firstthreshold read out from the storage unit when the reference internalimpedance was calculated, compares the reference internal resistance andthe second threshold read out from the storage unit when the referenceinternal resistance was calculated, and determines the SOH of thesecondary battery based on either of two comparison results.

A twentieth aspect of the present invention is an apparatus of thenineteenth aspect, in which the storage unit stores a charge ordischarge selection signal to select either the charge or the dischargeof the secondary battery with the specified current, and the controlunit reads the charge or discharge selection signal from the storageunit and outputs a specified instruction signal to the charging circuitor the discharging circuit based on the charge or discharge selectionsignal.

A twenty-first aspect of the present invention is an apparatus of thenineteenth or twentieth aspect, in which the storage unit stores a DC orAC selection signal to designate either an AC of 100 Hz or morefrequency or a pulse current as the specified current, and the controlunit reads the DC or AC selection signal from the storage unit andselects either the AC of 100 Hz or more frequency or the pulse currentin accordance with the DC or AC selection signal so as to output aspecified control signal to the charging circuit or the dischargingcircuit.

A twenty-second aspect of the present invention is an apparatus of thetwenty-first aspect, in which the storage unit stores at least one of afrequency of the AC and a pulse width of the pulse current, and thecontrol unit reads at least one of the frequency of the AC and the pulsewidth of the pulse current from the storage unit and sets at least oneof the frequency of the AC and the pulse width of the pulse current inthe charging circuit or the discharging circuit at the same time as orprior to the output of the specified control signal for the chargingcircuit or the discharging circuit.

A twenty-third aspect of the present invention is a power supply system,which includes the apparatus for determining an SOH of a secondarybattery of any one of the eighteenth to twenty-third aspects.

A twenty-fourth aspect of the present invention is a power supply systemof the twenty-third aspect, which further includes a display unit fordisplay a determination result of the SOH of the secondary battery byreceiving the result from the apparatus for determining an SOH of asecondary battery.

A twenty-fifth aspect of the present invention is a power supply systemof the twenty-third or twenty-fourth aspect, which further includes aninput unit for changing data stored in the storage unit, wherein atleast one or all of the first threshold for the determination, thesecond threshold for the determination, the charge or dischargeselection signal, the DC or AC selection signal, the frequency of theAC, and the pulse width of the pulse current can be changed with theinput unit.

A twenty-sixth aspect of the present invention is a method forestimating a deterioration level or a discharge capability of a batteryby comparing an impedance of the battery with a predetermined allowablerange thereof, the method including: measuring a current and a voltageof the battery; calculating an impedance Za of the battery from themeasured current value and the measured voltage value and calculating asuperimposed DC component IDCa from the measured current value; andestimating an impedance Zb of the case when a reference direct currentIDCb value is superimposed, from the calculated impedance Za value andthe calculated superimposed DC component IDCa value, based on apredetermined relational expression between a superimposed directcurrent IDC and a impedance Z so as to determine the deterioration levelor a discharge capability of the battery.

A twenty-seventh aspect of the present invention is a method of thetwenty-sixth aspect, in which, in the relational expression between thesuperimposed direct current IDC and the impedance Z, the impedance Z isexpressed by a function including at least one exponential term of thesuperimposed direct current IDC.

A twenty-eighth aspect of the present invention is a method oftwenty-seventh aspect, in which the relational expression between thesuperimposed direct current IDC and the impedance Z is expressed by:Z=a1×exp(−IDC/b1)+a2×exp(−IDC/b2)+ . . . +c.

A twenty-ninth aspect of the present invention is a method oftwenty-eighth aspect, in which the coefficients a1, a2, . . . , b1, b2,. . . of the relational expression between the superimposed directcurrent IDC and the impedance Z are given by functions f1(c), f2(c), . .. , g1(c), g2(c), . . . , of one adjustment parameter c, respectively.

A thirtieth aspect of the present invention is method of twenty-ninthaspect, in which a value of the adjustment parameter c is determined sothat, when substituting the calculated superimposed DC component IDCavalue into the direct current IDC of the relational expression, theimpedance Z of the relational expression agrees with the calculatedimpedance Za.

A thirty-first aspect of the present invention is a method of thetwenty-ninth or thirtieth aspect, in which the functions f1(c), f2(c), .. . , g1(c), g2(c), . . . of the adjustment parameter c are respectivelyexpressed by linear function of c.

A thirty-second aspect of the present invention is a method of any oneof the twenty-sixth to thirty-first aspects, in which the calculatedsuperimposed DC component IDCa value is obtained by performing any ofmoving average operation, Fourier transfer operation, and Kalman filteroperation on the measured current value.

A thirty-third aspect of the present invention is an apparatus forestimating a deterioration level or a charge capability of a batterybased on an impedance of the battery, which includes: a current sensorfor measuring a current of the battery; a voltage sensor for measuring avoltage of the battery; and a control unit for (i) receiving a measuredcurrent value and a measured voltage value from the current sensor andthe voltage sensor, respectively, (ii) calculating a impedance Za of thebattery from the measured current value and the measured voltage valueand calculating a superimposed DC component IDCa from the measuredcurrent value, (iii) estimating an impedance Zb of the case when areference direct current IDCb value is superimposed, from the calculatedimpedance Za value and the calculated superimposed DC component IDCavalue, based on a predetermined relational expression between asuperimposed direct current IDC and a impedance Z so as to determine thedeterioration level or a discharge capability of the battery.

A thirty-fourth aspect of the present invention is a power supplysystem, which includes the apparatus for estimating the deteriorationlevel or the discharge capability of the battery or the thirty-thirdaspect.

According to the present invention, when the detections of SOC and SOHare performed, the detections being interactive each other are set atthe same level, and the each other's data during the detections arerepeatedly obtained from each other and corrected by each other, wherebythe SOC and SOH are finally determined.

Besides, by storing the SOH in the memory, a detection error of each SOCand SOH and an abnormal detection can be detected by comparing thedetected values with the latest value or the value before the latest,etc., making it possible to conduct an appropriate management of thestorage battery.

According to the present invention, the SOH of the secondary battery isdetermined by correcting the temperature dependency of the internalimpedance or the internal resistance of the secondary battery by using atemperature characteristic function containing at least one exponentialterms and by estimating the reference internal impedance or thereference internal resistance at the predetermined referencetemperature, making it possible to determine the SOH accurately andcorrectly, regardless of the operating temperature.

In addition, the adjustment parameter of the temperature characteristicfunction is determined based on the measured current value, the measuredvoltage value, and the measured temperature value of the secondarybattery, making it possible to determine the SOH of the secondarybattery with high accuracy, corresponding to a change of temperaturecharacteristics due to the battery deterioration caused by aging, andthe like.

According to the present invention, it becomes possible to provide themethod and apparatus for estimating the deterioration level or thedischarge capability of the battery based on the estimation result ofthe impedance Zb at the reference direct current IDCb value and thepower supply system therewith, with the influences of thecharge/discharge current during the normal operation to the impedancebeing eliminated.

More specifically, the impedance Zb at the reference direct current IDCbvalue is obtained from the impedance Za and the DC component IDCa at thetime of measurement, and the impedance Zb is compared with the allowableimpedance value, thus the deterioration level or the dischargecapability of the battery can be determined at the same condition of thefixed DC value. As a result, it becomes possible to accurately determinethe deterioration level or the discharge capability of the battery.

Besides, since the relational expression between the superimposed directcurrent IDC and the impedance Z, which is required for obtaining theimpedance Zb at the reference direct current IDCb value based on theimpedance Za and the DC component IDCa at the time of measurement,includes at least one exponential term of the direct current IDC, itbecomes possible to determine the deterioration level or the dischargecapability of the battery with higher accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of an apparatusfor detecting SOH and SOC of a storage battery according to the firstembodiment of the present invention.

FIG. 2 is a characteristic chart showing the relationship between theinternal impedance and the OCV of the storage battery to be detected bythe apparatus according to the embodiment of the present invention.

FIG. 3 is a characteristic chart showing the relationship between SOCand OCV of the storage battery to be detected by the apparatus accordingto the embodiment of the present invention.

FIG. 4 is a characteristic chart showing the relationship between thetemperature and the internal impedance of the storage battery to bedetected by the apparatus according to the embodiment of the presentinvention.

FIG. 5 is a characteristic chart showing the relationship between theinternal impedance and the SOC of the storage battery to be detected bythe apparatus according to the embodiment of the present invention.

FIG. 6 is a characteristic chart showing a relationship between the SOHand the number of measurement times and also showing an example of anabnormal case of a new measured SOH detected by the apparatus accordingto the embodiment of the present invention.

FIG. 7 is a flow chart showing the method for detecting an SOH and of astorage battery according to the first embodiment of the presentinvention.

FIG. 8 is a block diagram illustrating a configuration of an apparatusfor detecting an SOH and SOC of a storage battery according to thesecond embodiment of the present invention.

FIG. 9 is a flow chart showing the method for detecting an SOH and SOCof a storage battery according to the second embodiment of the presentinvention.

FIG. 10 is a graph showing one example of temperature characteristic ofa secondary battery where the vertical axis indicates the internalimpedance and the horizontal axis indicates the temperature of thesecondary battery.

FIG. 11 is a block diagram illustrating the schematic configuration of apower supply unit for vehicles according to the third embodiment of thepresent invention.

FIG. 12 is a flow chart showing the operation process carried out mainlyby the controller 217.

FIG. 13 is a block diagram illustrating an embodiment of a power supplysystem for vehicles according to the present invention.

FIG. 14 is a flow chart for explaining one embodiment of a method forestimating a deterioration level or discharge capability of a batteryaccording to the present invention.

FIG. 15 is a block diagram illustrating a schematic configuration of apower supply system related to the fourth embodiment of the presentinvention.

FIG. 16 is a graph showing one example of a real part of the impedanceZa varying depending on the DC component IDCa.

FIG. 17 is a graph showing one example of an imaginary part of theimpedance Za varying depending on the DC component IDCa.

DESCRIPTION OF SYMBOLS

-   1: storage battery-   2: load-   3: discharging circuit-   4: charging circuit-   5: temperature sensor-   6, 7: ammeter-   10: SOH and SOC detection unit-   11: internal impedance measurement unit-   12: memory for internal impedance-   13: internal impedance correction unit-   14: internal impedance calculation unit-   15: battery temperature measurement unit-   16: memory for battery temperature-   17: OCV measurement unit-   18: memory for OCV value-   19: OCV value correction unit-   20: SOC calculation unit-   21: SOC output unit-   22: SOH output unit-   23: processing unit-   24: memory for SOC and SOH-   25: controller-   30: SOH and SOC detection unit-   31: charge-amount-change calculation unit-   32: SOC calculation unit-   201: point-   202: curve-   211: power supply unit for vehicles-   212: secondary battery-   213: current sensor-   214: voltage sensor-   215: temperature sensor-   216: discharging circuit-   217: control section-   218: memory-   219: path-   221: load-   222: alternator-   231: power supply system for vehicles-   232: input unit-   233: display unit-   311: power supply system-   312: battery-   313: alternator-   314: current sensor-   315: voltage sensor-   316: estimation unit-   317: discharging circuit-   318: line-   319: load-   320: control section

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An apparatus for detecting an SOH and an SOC of a storage batteryaccording to an embodiment of the present invention will be describedbelow.

First Embodiment

FIG. 1 is a block diagram illustrating an apparatus for detecting an SOHand an SOC of a storage battery according to the first embodiment of thepresent invention.

In FIG. 1, connected to a storage battery 1 is a discharging circuit 3controlling a current supplied from the storage battery 1 to a load 2, acharging circuit 4 for supplying a charge power, and an SOH and SOCdetection unit 10 for measuring SOH and SOC at open circuit.

The SOH and SOC detection unit 10 has an internal impedance measurementunit 11, a memory 12 for internal impedance, an internal impedancecorrection unit 13, a battery temperature measurement unit 15, a memory16 for battery temperature, an open circuit voltage (OCV) measurementunit 17, a memory 18 for OCV value, an OCV value correction unit 19, astate of charge (SOC) calculation unit 20, and an internal impedancecalculation unit 14. The internal impedance measurement unit 11 isconnected to a positive electrode and a negative electrode of thestorage battery 1 and measures an internal impedance of the storagebattery 1. The memory 12 for internal impedance stores the internalimpedance data. The internal impedance correction unit 13 acquires theinternal impedance data from the memory 12 for internal impedance andcorrects the data based on a battery temperature. The batterytemperature measurement unit 15 measures a temperature of the storagebattery 1 based on the output signal from a temperature sensor 5attached to the storage battery 1. The memory 16 for battery temperaturestores the battery temperature data of the storage battery 1. The OCVmeasurement unit 17 is connected to the both electrodes of the storagebattery 1 and measures OCV. The memory 18 for OCV value stores the OCVmeasured values by the OCV measurement unit 17. The OCV value correctionunit 19 corrects the measured data stored in the memory 18 for OCV valuein accordance with the internal impedance. The SOC calculation unit 20calculates SOC based on the OCV value corrected by the OCV valuecorrection unit 19. The internal impedance calculation unit 14 furthercorrects the corrected value of the internal impedance being output fromthe internal impedance correction unit 13 based on the SOC.

The memory 12 for the internal impedance is configured to: output setvalues stored therein to the OCV value correction unit 19 via the switch29 (Route 1 shown in FIG. 1) in the case of the first measurement of theinternal impedance in every ridings by the internal impedancemeasurement unit 11; and output a measured value R1 of the internalimpedance measured by the internal impedance measurement unit 11 to theinternal impedance correction unit 13 in the case of the second or latermeasurement in every ridings. The set values of the internal impedanceinclude an initial value R₀ set in advance in the memory 12 and aprevious last corrected value R″_(prev) lastly obtained in the previouscorrection by the internal impedance calculation unit 14 and stored inthe memory 12. Only in the case of the first measurement of the internalimpedance of the new battery, the memory 12 outputs the initial value R₀to the OCV value correction unit 19 as the set value, and in the case ofthe later measurement, the memory 12 outputs the previous last correctedvalue R″_(prev) as the set value. It should be noted that the initialvalue R₀ is an internal impedance value at a reference temperature Txand a reference SOC value N₀.

The internal impedance value is defined as the SOH because an internalimpedance increases associated with deterioration of the storage battery1.

The OCV value correction unit 19 is configured to receive either one ofthe initial value R₀ and the previous last corrected value R″_(prev) ofthe internal impedance from the memory 12 by the Route 1 as describedabove and also receive a corrected internal impedance value R″_(x) (x=1,2, . . . , n−1) from the internal impedance calculation unit 14 by theRoute 2, by turning the switch 29. The corrected internal impedancevalue R″_(x) is described herein after in detail. Further, the OCV valuecorrection unit 19 receives a measured OCV value V₁ from the memory 18for OCV value, and then corrects the measured OCV value V₁ of thestorage battery 1 to a value V₀ at the initial state based on therelationship between the internal impedance and the OCV valueexemplified in FIG. 2.

The SOC calculation unit 20 receives a corrected OCV value from the OCVvalue correction unit 19 and calculates an SOC value by substituting thecorrected OCV value into a function expressing a relationship betweenOCV and SOC of the storage battery 1 at the initial state as exemplifiedin FIG. 3, and then outputs the calculated SOC value N_(x) (x=1, 2, . .. , n) to internal impedance calculation unit 14. The SOC calculationunit 20 repeats this SOC calculation a prescribed n times of at leasttwo (i.e. n indicates a repeat number of the SOC calculation) so as toobtain the last (nth) calculated SOC value N_(n). The last calculatedSOC value N_(n) is output to both a processing unit 23 (e.g. a display)and a memory 24 for SOC and SOH via an SOC output unit 21. The SOCcalculation described above is repeated until, for example, the SOHconverges to a specified range.

As the function shown in FIG. 3 includes temperature of the storagebatter 1 as a conditioning factor of the variation, the function iscorrected based on the value of the temperature by receiving a measuredtemperature value from the memory 16 for battery temperature. Further,as the function varies with the internal impedance, the function may becorrected based on the corrected internal impedance value corrected bythe internal impedance calculation unit 14.

The internal impedance correction unit 13 receives the measured internalimpedance R₁ of the storage battery 1 measured by the internal impedancemeasurement unit 11 via the memory 12 for internal impedance and alsoreceives the measured value of the battery temperature from the memory16 for battery temperature. Then, the internal impedance correction unit13 makes a correction of converting the internal impedance R₁ at themeasurement temperature T₁ into an internal impedance R′ at thepredetermined temperature T₀ (for example, the normal temperature) basedon the relationship between the internal impedance and the temperatureexemplified in FIG. 4, further outputs the converted internal impedancevalue R′ to the internal impedance calculation unit 14. The relationshipbetween the internal impedance and the temperature shown in FIG. 4 isunder the condition of the reference SOC value N₀.

The internal impedance calculation unit 14 receives the converted valueR′ by the internal impedance correction unit 13 and the calculated valueN_(x) by the SOC calculation unit 20, and corrects the convertedinternal impedance value R′ at the reference SOC N₀ to the internalimpedance value R″_(x) at the calculated SOC value N₀ according to therelationship between the SOC and the internal impedance value under thepredetermined temperature as exemplified in FIG. 5. Further, theinternal impedance calculation unit 14 repeats the correction of theinternal impedance the n times (n corresponds to the repeat number ofthe SOC calculation by the SOC calculation unit 20), and outputs thecorrected internal impedance values R″₁ to R″_(n-1) obtained in thefirst to the (n−1)th corrections to the OCV value correction unit 19 viathe switch 29 and outputs the last (nth) corrected internal impedancevalue R″_(n) obtained in the nth correction to an SOH output unit 22.

The SOH output unit 22 defines the last corrected internal impedancevalue R″_(n) as the state of health (SOH) and outputs the value R″_(n)to the processing unit 23 and the memory 24 for SOC and SOH.

The controller 25 directs a measurement timing for the internalimpedance measurement unit 11, the battery temperature measurement unit15 and the OCV measurement unit 17, and also directs an input signalselection for the switch 29. Further, the controller 25 sets a value ofthe predetermined temperature to the memory 16 for battery temperatureand writes the initial value R₀ of the internal impedance, the referenceSOC value N₀, and the last corrected internal impedance value R″_(n)corrected by the internal impedance calculation unit 14 into the memory12 for internal impedance. The last corrected internal impedance valueR″_(n) written in the memory 12 will be taken out therefrom as theprevious last corrected value R″_(prev) in the next measurement of theinternal impedance.

Furthermore, the controller 25 stores the coefficients and functionsexpressed by the characteristics in FIG. 2 through FIG. 5 to theinternal impedance correction unit 13, the internal impedancecalculation unit 14, the OCV value correction unit 19, and the SOCcalculation unit 20 and sets the repeat number of the internal impedanceand SOC calculations in the internal impedance calculation unit 14 andthe SOC calculation unit 20.

Further, the controller 25 determines (i) a slope of a relationalexpression between SOH values (the internal impedance values) stored inthe memory 24 and the number of measurement times as shown in FIG. 6 and(ii) threshold values indicating an allowable range. Further, when anewly input SOH data is out of the allowable range, the controlleroutputs a detection instruction signal again to the OCV measurement unit17, the battery temperature measurement unit 15, the internal impedancemeasurement unit 11 and the like, or issues an alert judging asabnormal.

The conditions such as the initial value and the reference SOC value N₀,each correction coefficients, each characteristic and the like arestored in a memory of a computer, and processes such as the calculation,the correction, and the like are carried out according to programsstored in the memory of the computer.

Next, a method for detecting an SOH and an SOC of the storage battery 1using the above-described SOC and SOH detection unit 10 will beexplained according to the flow chart shown in FIG. 7.

First, either one of the initial value R₀ of the internal impedance atthe reference SOC value N₀ and the previous last corrected valueR″_(prev) of the internal impedance lastly obtained in the previouscorrection is set to the memory 12 for internal impedance, and thepredetermined temperature T₀ necessary for correcting the internalimpedance is written in the memory 16 for battery temperature. Further,the correction coefficient of temperature based on FIG. 4 is set in theinternal impedance correction unit 13, the correction coefficient of theSOC value based on FIG. 5 is set in the internal impedance calculationunit 14, an the relationship between the OCV and the corrected internalimpedance based on FIG. 2 is set in the OCV value correction unit 19,and a function expressing a relationship between the OCV and the SOCbased on FIG. 3 is set in the SOC calculation unit 20. These processesare controlled by the controller 25 (FIG. 7, S10).

Next, according to a instruction signal from the controller 25, thebattery temperature measurement unit 15 and the OCV measurement unit 17perform the measurements of temperature and OCV, respectively, and then,the measured temperature value is stored in the memory 16 for batterytemperature, and the measured OCV value is stored in the memory 18 forOCV value (FIG. 7, S11 and S12).

Continuously, the OCV value correction unit 19 acquires either one ofthe set values of the internal impedance from the memory 12 for internalimpedance through the switch 29 (FIG. 7, S13), and then, corrects themeasured OCV value into, for example, an OCV value in the initial stateof the storage battery 1, based on the correction coefficient of theinternal impedance according to FIG. 2 (FIG. 7, S14).

Here, only in the case of the first measurement of the internalimpedance of the new battery by the internal impedance measurement unit11, the set internal impedance value to be acquired by the OCV valuecorrection unit 19 is the initial value R₀ set in advance, and in thecase of the later measurement, the set internal impedance value is theprevious last corrected value R″_(prev) lastly obtained in the previouscorrection by the internal impedance calculation unit 14.

As shown in a dashed line between the memory 18 for OCV value and theSOC calculation unit 20 in FIG. 1, the measured OCV value may be inputdirectly to the SOC calculation unit 20, by omitting the correction ofthe OCV value using the set value of the internal impedance.

The internal impedance correction unit 13 acquires the newest measuredvalue of the internal impedance of the storage battery 1 measured by theinternal impedance measurement unit 11 (FIG. 7, S15) from the memory 12for internal impedance, further acquires the measurement temperature T₁of temperature of the storage battery 1 from the memory 16 for batterytemperature. As the measured internal impedance value is the value R₁ atthe actual temperature of the storage battery 1 on measuringtemperature, the internal impedance correction unit 13 makes correctionof converting the internal impedance R₁ at the measurement temperatureT₁ into the converted internal impedance R′ at the predeterminedtemperature T₀ (for example, the normal temperature), using thecorrection coefficient of temperature based on FIG. 4, (FIG. 7, S16).The converted value R′ is the value under the condition of the referenceSOC value N₀.

The measurement of the internal impedance is performed by the internalimpedance measurement unit 11 according to the instruction from thecontroller 25, and the measured value R₁ is stored in the memory 12 forinternal impedance (FIG. 7, S15).

On the other hand, the SOC calculation unit 20 calculates the first SOCvalue N₁ by substituting either one of the corrected OCV value by theOCV value correction unit 19 and the measured value into the pre-setfunction expressing the relationship between the OCV and the SOC asshown in FIG. 3 (FIG. 7, S14 and S17).

Next, the internal impedance calculation unit 14, using the correctioncoefficient expressing the relationship between the SOC and the internalimpedance at the predetermined temperature T₀ as shown in FIG. 5,calculates a new internal impedance (FIG. 7, S18). That is, theconverted internal impedance value R′ at the SOC value N₀ input from theinternal impedance correction unit 13 is further corrected to theinternal impedance value R″₁ at the first SOC N₁.

Then, the OCV value correction unit 19, using the internal impedancecorrected value R″₁ output from the internal impedance calculation unit14, corrects the measured OCV value again, and outputs the OCV correctedvalue to the SOC calculation unit 20 (FIG. 7, S19 and S14).

The SOC calculation unit 20 further calculates the second SOC value N₂based on the corrected OCV value, and outputs the second calculatedvalue N₂ to the internal impedance calculation unit 14 (FIG. 7, S17).The internal impedance calculation unit 14 receives the secondcalculated SOC value N₂, and then, makes the second correction of theinverted value R′ output from the internal impedance correction unit 13,and outputs the second internal impedance corrected value R″₂ (FIG. 7,S18).

The SOC calculation unit 20 repeats the above-described SOC calculationthe prescribed n times, and the internal impedance calculation unit 14repeats the correction the prescribed n times based on the calculatedSOC value (FIG. 7, S20 and S21). Thereafter, the controller 25 definesthe last corrected value R″_(n) of the internal impedance by theinternal impedance calculation unit 14 as the SOH value, and allows theinternal impedance correction unit 14 to output the SOH value to boththe memory 24 for SOC and SOH and the processing unit 23 via the SOHoutput unit 22 (FIG. 7, S22). Further, the controller 25 defines thelast calculated SOC value N_(n) by the SOC calculation unit 20 as theSOC value, and allows the SOC calculation unit 20 to output the SOC toboth the memory 24 for SOC and SOH and the processing unit 23 via theSOC output unit 21 (FIG. 7, S23).

The SOH value is output from the SOH output unit 22, whereby the memory18 for OCV value deletes data of the OCV value.

Then, the controller 25 determines an approximate line showing thechange of the SOH with respect to the number of measurement times asshown in, for example, FIG. 6 where the horizontal axis indicates thenumber of measurement times and the vertical axis indicates the SOH. Aplurality of points corresponding to the number of measurement times,preferably three or more points, are plotted in the graph. Thecontroller 25 determines the approximate line based on the plottedgraph, and determines whether or not the newest measured SOH valueexists or converges within a certain allowable range (between thethreshold values “b”) including the approximate line “a”. When being outof the allowable range, the controller 25 allows removing the newestmeasured SOH value from the memory 24 for SOC and SOH as an abnormalvalue and allows the respective units to carry out the detections of theSOC and SOH again (FIG. 7, S25). If showing the abnormal value, theforced re-measurement is performed one time or more.

For example, for a sealed lead-acid battery having 5.5 Ah of 5-hour ratecapacity in the environmental conditions of −30 degrees C., in the casewhere the increase of the internal impedance (the SOH) is 2 mΩ/month atthe last period of the deterioration of the storage battery, if thedetected SOH is 5 m Ω or more away from the approximate line, it can bedetermined that the detected SOH is abnormal as a measurement valueafter one month. Therefore, the re-detection is carried out.

When showing the abnormal value, it may perform other processing thanthe re-detection, for example, issuance of a warning such as sounding analert and displaying a message.

On the other hand, in the case where the SOH value falls within theallowable range, the SOH value stored in the memory 24 for SOC and SOHis decided as the true value.

As described above, when the detections of SOC and SOH are performed,the detections being interactive each other are set at the same level,and the each other's data during the detections are repeatedly obtainedfrom each other and corrected by each other, whereby the SOC and SOH arefinally determined.

Accordingly, the SOC and SOH can be detected at almost the same timewith high accuracy.

Further, with the SOH being stored in the memory (i.e., storage medium),a detection error of each SOC and SOH and an abnormal detection can bedetected by comparing the detected values with the latest value or thevalue before the latest, etc., making it possible to conduct anappropriate management of the storage battery.

Second Embodiment

FIG. 8 is a block diagram illustrating a configuration of an apparatusfor detecting SOH and SOC of a storage battery related to the secondembodiment of the present invention. In FIG. 8, the same parts as inFIG. 1 are designated by the same symbols.

In FIG. 8, the storage battery 1 is connected to the load 2 via thedischarging circuit 3 and further connected to the charging circuit 4and an SOH and SOC detection unit 30. Connected between the chargingcircuit 4 and the storage battery is a first ammeter 6. Connectedbetween the load 2 and the storage battery 1 is a second ammeter 7.

The SOH and SOC detection unit 30, as the same as shown in the abovementioned embodiment, has the internal impedance measurement unit 11,the memory 12 for internal impedance, the internal impedance correctionunit 13, the battery temperature measurement unit 15, the memory 16 forbattery temperature, the switch 29, the SOC output unit 21, and the SOHoutput unit 22.

Further, the SOH and SOC detection unit 30 has a charge-amount-changecalculation unit 31 and an SOC calculation unit 32. Thecharge-amount-change calculation unit 31 calculates both a change in thecharge amount and a change in the SOC value in a prescribed time period,based on the product of time and both the charge current and thedischarge current detected by the first and second ammeters 6 and 7. TheSOC calculation unit 32 corrects the change in the SOC value inaccordance with the internal impedance value and adds the correctedchange in the SOC value to a previous last calculated SOC value beingstored in memory 24 for SOC and SOH, so as to output it as an SOC outputvalue.

The SOC calculation unit 32 is configured to receive the internalimpedance value from either the memory 12 for internal impedance or theinternal impedance calculation unit 14 through the switch 29 and tooutput the calculated SOC value to the internal impedance calculationunit 14.

Further, the last calculated SOC value obtained after repeating the SOCcalculation the prescribed n times of at least two by the SOCcalculation unit 32 is output to the processing unit 23 and the memory24 for SOC and SOH thorough the SOC output unit 21.

Next, a method for detecting SOH and SOC of the storage battery 1 withthe SOC and SOH detection unit 10 described above will be explainedaccording to the flow chart shown in FIG. 9.

First, as explained in the above-described first embodiment, theinternal impedance correction unit 13 makes the correction of convertingthe measured internal impedance R₁ stored in the memory 12 for internalimpedance into the internal impedance R′ based on temperature (FIG. 9,S30, S32, S35, and S36).

The converted internal impedance value R′, as the same as theabove-mentioned first embodiment, is further corrected by the internalimpedance calculation unit 14 based on the SOC value N_(x) output fromthe SOC calculation unit 32, so that the corrected internal impedanceR″_(x) is obtained. After repeating the correction of the internalimpedance R′ the prescribed n times, the last corrected value R″_(n)being defined as the SOH is output from the SOH output unit 22 (FIG. 9,S41, SS42, and S43).

Further, the charge-amount-change calculation unit 31 calculates boththe charge in the charge amount and the change in the SOC value in apredetermined time period, based on the product of time and both thecharge current and the discharge current detected by the first andsecond ammeters 6 and 7 (FIG. 9, S31 and S34). In this case, thedischarge current is represented as negative, and the charge current isrepresented as positive.

Meanwhile, since a full-charge capacity of the storage battery 1 changesdepending on the SOH of the storage battery 1, the change in the SOCvalue calculated by the charge-amount-change calculation unit 31 isfurther corrected by the SOC calculation unit 32, based on either one ofthe initial value R₀ set in advance and the previous last correctedvalue R″_(prev) lastly obtained in the previous correction which areoutput from the memory 12 for internal impedance (FIG. 9, S37). Thecorrection based on the initial value R₀ may be omitted.

Further, in the SOC calculation unit 32, the corrected change in the SOCvalue is added to either one of the initial value thereof and theprevious last calculated SOC value obtained in the previous calculationstored in the memory 24 for SOC and SOH, whereby the SOC calculationunit 32 calculates a new SOC (FIG. 9, S38). The previous last calculatedSOC value lastly obtained in the previous calculation has been takenfrom the memory 24 for SOC and SOH and has been written to the memory 12for internal impedance by the controller 25.

The newly calculated SOC value is transmitted to the internal impedancecalculation unit 14. Then, the internal impedance calculation unit 14corrects the internal impedance value R′ based on the newly calculatedSOC value and outputs the corrected internal impedance value R″_(x) tothe SOC calculation unit 32 through switch 29 (FIG. 9, S41).

The calculation of the SOC value is repeated a prescribed n times by theSOC calculation unit 32 and the last calculated SOC value is output bythe SOC output unit 21 (FIG. 9, S38, S39, and S40).

The SOC value and the SOH value calculated by means of the above processare output to the memory 24 for SOC and SOH and the processing unit 23as the same of the above embodiment (FIG. 9, S40 and S43).

Further, the controller 25, as the same of the above-mentioned firstembodiment, determines an approximate line showing the change of the SOHwith respect to the number of measured times, based on the plotted graphin which a plurality of points corresponding to the number ofmeasurement times, preferably three or more points, are plotted, wherethe horizontal axis indicates the number of measurement times and thevertical axis indicates the SOH. Further, the controller 25 determineswhether or not the newest measured value exists or converges within acertain allowable range including the approximate line. When being outof the allowable range, the controller 25 allows removing the newestmeasured value from the memory 24 for SOC and SOH as an abnormal valueand allows the respective units to carry out the detections of SOC andSOH again (FIG. 9, S44). When showing the abnormal value, the forcedre-measurement is performed one time or more. Alternatively, it mayperform other processing than the re-detection, for example, issuance ofa warning such as sounding an alert and displaying a message.

On the other hand, in the case where the SOH value falls within theallowable range, the SOH stored in the memory 24 for SOC and SOH isdecided as the true value.

As explained above, when the detections of SOC and SOH are performed,the detections being interactive each other are set at the same level,and the each other's data during the detections are repeatedly obtainedfrom each other and corrected by each other, whereby the SOC and the SOHare finally determined. This makes it possible to detect the SOC and theSOH at almost the same time with high accuracy.

Further, with the SOH value being stored in the memory (i.e., storagemedium), a detection error of each SOC and SOH and an abnormal detectioncan be detected by comparing the detected values with, for example, thelast calculated value obtained in the previous calculation or obtainedtherebefore, making it possible to conduct an appropriate management ofthe storage battery.

In detections of SOC and SOH, each other's measured value is mutuallyaffected, and both detections, i.e. both measurement values, can not beuniquely determined but is determined depending on the temperature anddetected information of another side. According to this embodiment, asdescribed above, since the measured SOC and SOH are mutually used as adetection condition, the high-accuracy detection can be achieved enoughto satisfy a user.

Third Embodiment

Next, a method and an apparatus for detecting deterioration of asecondary battery and a power supply system therewith according to apreferable embodiment of the present invention will be explained indetail with reference to drawings.

Hereinafter, there will be explained an embodiment in the case where thepresent invention is applied to a power supply unit for vehicles andpower supply system for vehicles having a function of determining adeterioration of a secondary battery mounted on a vehicle and the like.

FIG. 11 is a block diagram illustrating the configuration of a powersupply unit according to the third embodiment of the present invention.In FIG. 11, a power supply unit 211 for vehicles includes a secondarybattery 212, a current sensor 213 for measuring a current of thesecondary battery 212, a voltage sensor 214 for measuring a voltage ofthe secondary battery, and a temperature sensor 215 for measuring atemperature of the secondary battery 212. The unit also includes adischarging circuit 216, a controller 217, and a memory 218, todetermine the deterioration of the secondary battery 212.

The power supply unit 211 for vehicles is connected to an alternator 222and a load 221 consisting of various electric devices for a vehicle andis configured such that the electric power is supplied to the load 222from either the secondary battery 212 or the alternator 222. Thealternator 222 also supplies a charging electric power to the chargesecondary battery 212.

The power supply unit 211 for vehicles having a configuration as shownin FIG. 11 allows the secondary battery 212 to be charged or bedischarged with a specified current and timing to determine SOH of thesecondary battery 212. In the case where the secondary battery 212 isdischarged with a specific current, the discharge is carried out byconnecting the discharging circuit 216 to the secondary battery 212. Inthe case where the secondary battery 212 is charged, the current issupplied from alternator 222 to the secondary battery 212. In otherwords, the alternator 222 is employed as a charging circuit in thisembodiment. In this case, the current is allowed to flow through a path219 to bypass the discharging circuit 216.

When the secondary battery 212 is charged or discharged as describedabove, a current and a voltage at that time are measured by the currentsensor 213 and the voltage sensor 214, respectively, and the measuredcurrent value and the measured voltage value are sent to the controller217.

After the controller 217 receives the measured current value and themeasured voltage value from the current sensor 213 and the voltagesensor 214, respectively, the controller 217 determines the SOH bycalculating the internal impedance or the internal resistance of thesecondary battery 212 based thereon by using the method describedhereinafter. The controller 217 also judges as to whether discharging orcharging the secondary battery with the specified current and timing andthen controls on/off of the connection between the discharging circuit216 and the secondary battery 212 based on the judged result.

As for judging as to whether discharging or charging the secondarybattery 212 with the specified current, it may be practicable that, forexample, a charge or discharge selection signal is pre-set in the memory218, and the controller 217 reads the charge or discharge selectionsignal from memory 218 so as to judge as to whether charging ordischarging the secondary battery 212.

The power supply unit 211 for vehicles of the present invention alsoincludes the temperature sensor 215. The temperature sensor 215 isarranged near the secondary battery 212 and measures the temperature ofthe secondary battery 212 to send the measured temperature to thecontroller 217.

In this embodiment, an AC of 100 Hz or above frequency, or a pulsecurrent is used as the specified current when carrying out the charge ordischarge of the secondary battery 212. It is noted that, when using thepulse current, the measured values of current and voltage measuredwithin 10 ms of applying the pulse current is used for the calculationof the internal resistance. The specified current described above makesit possible to eliminate the influence of the noise from the alternator222 or the load 221 as much as possible.

The selection of either the AC of 100 Hz or above frequency or the pulsecurrent can be carried out by the controller 217, based on DC or ACselection signal read from the memory 218. In order to apply the AC of100 HZ or above frequency from the alternator 222 to secondary battery212, it is required that the power supply unit is provided with aspecified charging circuit instead of the path 219.

Next, the temperature characteristic of the internal impedance or theinternal resistance of the secondary battery 212 will be explained byusing FIG. 10. FIG. 10 is a graph showing one example of the temperaturecharacteristic of the secondary battery where the vertical axisindicates the internal impedance and the horizontal axis indicates thetemperature of a secondary battery. In FIG. 10, points 201 respectivelyindicate the magnitude of the internal impedance measured at eachtemperature.

In the example shown in FIG. 10, each of the internal impedance of thesecondary battery 212 was measured by using the AC of 100 Hz frequency.

According to FIG. 10, it is recognizable that the internal impedance ofthe secondary battery increases with lowering the temperature,especially, dramatically increases at below the freezing point. Thetemperature characteristic shown in the FIG. 10 shows that the internalimpedance changes depending on a time period of using the secondarybattery and that there is the deterioration caused by aging such thatthe internal impedance increases with time of using the battery.Although the characteristic of the internal impedance was explained inthe above-described example, the internal resistance measured by usingthe DC also has the same temperature characteristic.

Generally, the secondary battery 212 for vehicles is used at wide-rangetemperature, it is required that the secondary battery 212 should havean appropriate internal impedance and the internal resistance at a rangeof operating temperature. Therefore, when the controller 217 in thepower supply unit 211 for vehicles 211 determines the SOH of thesecondary battery 212, it is important that the temperaturecharacteristics of the internal impedance or the internal resistance ofthe secondary battery 212 described above can be evaluated accurately.

Accordingly, in the method of determining SOC of a secondary batteryaccording to the present invention, a specified temperaturecharacteristic function accurately expressing the temperaturecharacteristic of the internal impedance or the internal resistance ofthe secondary battery 212 is generated beforehand for use. In the methodfor determining SOH of a secondary battery according to the presentinvention, a temperature of the secondary battery 212 is measured at thesame time when measuring the current and the voltage, and an internalimpedance or an internal resistance of the secondary battery 212calculated by the measured current value and measured voltage value areconverted to an internal impedance or an internal resistance atspecified reference temperature by using the specified temperaturecharacteristic function.

The temperature characteristic function used in the method fordetermining SOH of a secondary battery according to the presentinvention is characterized by containing at least one exponential termsand one adjustment parameter. One example of the temperaturecharacteristic function is shown in the following expression (1).Z(Temp) or R(Temp)=f(C)×exp{g(C)/Temp}+C  (1)where Z is the internal impedance of the secondary battery 212, R is theinternal resistance of the secondary battery 212, Temp is thetemperature of the secondary battery 212, C is the adjustment parameter,and f and g are functions of C

The expression (1) contains only one exponential term, however, maycontain further exponential terms. In any way, the number of exponentialterms and the functional forms of the functions f (C) and g (C) may bedecided such that the expression (1) can accurately express the internalimpedance Z or the internal resistance R of the secondary battery 12. InFIG. 10, a curve 202 indicates one example of the temperaturecharacteristic function expressed by the expression (1).

A concrete functional form of a temperature characteristic functionindicated by the curve 202 is shown in the following expression (2).Z(Temp)=5.435×exp{−22.81/Temp}+8.176   (2)

C, f and g in the expression (2) are respectively set as follows:C=8.176   (3)f(C)=0.6648×C=5.435   (4)g(C)=−2.790×C=−22.81   (5)

As shown in the FIG. 10, the internal impedance (a curve 202) calculatedby using the expression (2) agrees with the measured values (points 201)very well, and R²=0.99854.

In the method of determining SOH of a secondary battery according to thepresent invention, a first internal impedance Z or a first internalresistance R are calculated based on the measured current value andmeasured voltage value when the secondary battery is discharged orcharged. Since a temperature of the secondary battery is also measuredat that time, the value of the adjustment parameter C is decided bysubstituting the internal impedance Z or the internal resistance R thuscalculated and the measured temperature value Temp into the expression(1).

The temperature characteristic of the internal impedance or the internalresistance of the secondary battery varies depending on thedeterioration caused by aging from the start of use and the like. Theadjustment parameter C is a parameter for allowing the expression (1) toagree with the temperature characteristic at the time by adjusting thevariation of the temperature characteristic depending on thedeterioration caused by aging, and the like.

After the adjustment parameter C is decided, a specified referencetemperature Tx is substituted into Temp of the expression (1) using thedecided value C. As a result, the internal impedance or the internalresistance at the specified reference temperature Tx is calculated byusing the expression (1). Then, the SOH of the secondary battery 121 canbe determined by comparing the calculated internal impedance or thecalculated internal resistance with a specified threshold.

Next, there will be explained one example of concrete process flow forperforming the determination of SOH of the secondary battery 212 inpower supply unit 211 for vehicles according to the present invention.FIG. 12 is a flow chart showing the operation process carried out mainlyby the controller 217. The operation process shown in FIG. 12 is startedin the power supply unit 211 for vehicles at a specified timing beingset in advance. Although FIG. 12 shows an example of performing thedetermination of SOH of the secondary battery 212 based on the internalimpedance, if performing the determination of the SOH based on theinternal resistance, the internal impedance may be replaced by theinternal resistance in FIG. 12.

In FIG. 12, when reaching the specified timing, the operation process atthe controller 217 is started. First, an initial setting of parametersnecessary for the operation process is carried out at the step S101.Setting values of each parameter may be set by reading pre-set valuesfrom the memory 218 at the step S101.

Parameters to be set at the step S101 includes the reference temperatureTx for estimating the internal impedance or the internal resistance,determination thresholds Zth and Rth with respect to the internalimpedance and the internal resistance for determining the SOH of thesecondary battery 212, and the like. The charge or discharge selectionsignal and the DC or AC selection signal as well may be read from thememory 218 at the step S101. In the case where the controller 217 givesinstructions for discharging or charging the secondary battery to thedischarging circuit 216 or the alternator 222, an AC frequency or apulse width of a pulse current may be read from the memory 218 so as toexecute the initial setting at the step S101.

Appropriate initial setting values in accordance with the characteristicof the secondary battery 212 can be fixed in advance, but the initialsetting values may be changeable as needed depending on the operatingsituations, the deterioration caused by aging of the secondary battery212, and the like.

Next, at the step S102, the discharging circuit 216 or the alternator222 allow the secondary battery to be charged or discharged with thespecified current of the AC or a pulse current, and the measured currentvalue and the measured voltage value are acquired from the currentsensor 213 and the voltage sensor 214, respectively, at a specifiedtiming.

At the step S103, the internal impedance Z of the secondary battery 212is calculated by means of the Fourier expansion and the like, using themeasured current value and measured voltage value acquired at the stepS102. The internal resistance R can be calculated by using theexpression of R=dV/dI, where dV and dI are the voltage change and thecurrent change, respectively, during a specified time period dt notexceeding 10 ms of starting the discharge or the charge of a pulsecurrent.

Next, at the step S104, a measured temperature value Tp of the secondarybattery 212 at the time when the discharge or the charge is performed isinput from the temperature sensor 215. Then, at the step S105, thecalculated internal impedance Z calculated at the step S103 and themeasured temperature value Tp input at the step S104 are substitutedinto the expression (1) so as to calculate the value of the adjustmentparameter C.

Next, at the step S106, using the reference temperature Tx set at thestep S101 and the adjustment parameter C calculated at the step S105,the internal impedance Zx at the reference temperature Tx is calculatedby using the following expression (6).Zx(Tx)=f(C)×exp{g(C)/Tx}+C  (6)

Next, at the step S107, the internal impedance Zx at referencetemperature Tx calculated at step S06 is compared with the determinationthreshold Zth set at the step S101, thereby judging which of the Zx andZth is high. Then, if the internal impedance Zx is judged as being equalto or less than Zth, i.e. Zx≦Zth, the secondary battery is determined asnot being deteriorated and the processing is completed.

On the contrary, if the internal impedance Zx is judged as exceedingZth, i.e. Zx>Zth, the secondary battery 212 is determined as beingpossible to be deteriorated. In the method for determining SOH of thisembodiment shown in FIG. 12, in order to ensure the SOH determinationfor the secondary battery 212, the secondary battery 212 is determinedas being deteriorated only when the determination at the step S107 isrepeated a prescribed number of times consecutively.

More specifically, if it is determined at the step S107 as being thatthere is a possibility of the deterioration of the secondary battery212, it is determined at the step S108 as to whether or not thedetermination is repeated the prescribed number of times consecutively.If the secondary battery 212 is determined as being deteriorated theprescribed number of times consecutively as a result of thedeterminations, the process proceeds to the step S109 and the SOHdetermination of the secondary battery 212 is executed. As describedabove, the reason of the confirmation as to whether or not the SOHdetermination is repeated a prescribed number of times consecutively isfor preventing the influence of the variation of the internal impedanceso as to stabilize the judgment result.

Next, a power supply system for vehicles provided with a power supplyunit for vehicles according to the present invention will be explainedbelow. FIG. 13 is a block diagram illustrating the present embodiment ofa power supply system for vehicles according to the present invention. Apower supply system 231 for vehicles includes the power supply unit forvehicles 211, an input unit 232, and a display unit 233.

The input unit 232 and the display unit 233 are connected to thecontroller 217 and are configured such that data is input thereto andoutput therefrom. In the case where the secondary battery 212 isdetermined as being deteriorated at the step S109, the result is sentfrom the controller 217 to the display unit 233 so as to be displayedthereon. This makes it possible to notify the driver of thedeterioration of the secondary battery 212.

The input unit 232 is usable for setting, for example, the determinationthreshold for the internal impedance of the secondary battery 212, thedetermination threshold for the internal resistance, the charge ordischarge selection signal, the DC or AC selection signal, the ACfrequency, and the pulse width of the pulse current, into the memory218. In the embodiment shown in FIG. 13, each data is set into thememory 218 through the controller 217.

The power supply system for vehicles configured as described aboveenables the prompt and clear notification to the driver of thedeterioration of the secondary battery. Further, the various settingvalues is easily changeable by using the input unit 232, making itpossible to carry out the proper treatment depending on the operatingsituations, the deterioration of the secondary battery 212 caused byaging, and the like.

In the above-described embodiment, while the power supply system forvehicles having the configuration for determining the deterioration ofthe secondary battery for vehicles mounted on a vehicle was explained,the present invention is not limited to a secondary battery for vehiclesand can be widely applied to various power supply systems provided witha general secondary battery.

Fourth Embodiment

A method for estimating a deterioration level or a discharge capabilityof a battery according to the present invention includes: calculating animpedance Za of a battery from the measured current value and themeasured voltage value of the battery and calculating a superimposed DCcomponent IDCa from the measured current value; and estimating animpedance Zb in the case when a reference direct current IDCb value issuperimposed, from the calculated impedance Za value and the calculatedsuperimposed DC component IDCa value, based on a predeterminedrelational expression between a superimposed direct current IDC and aimpedance Z so as to determine the deterioration level or the dischargecapability of the battery.

Preferably, in the above relational expression between the superimposeddirect current IDC and the impedance Z, the impedance Z is expressed bya function having at least one exponential term of the superimposeddirect current IDC. Especially, the following relational expression (7)is preferable.Z=a1×exp(−IDC/b1)+a2×exp(−IDC/b2)+ . . . +c  (7)

FIG. 15 is a block diagram illustrating a schematic configuration of apower supply system according to the forth embodiment of the presentinvention. In FIG. 15, a power supply system 311 includes a battery 312and an alternator 313 as a power supply. An estimation unit 316 forestimating at least one of the deterioration level and the dischargecapability includes a current sensor 314 and a voltage sensor 315 formeasuring a current and a voltage of the battery 312, respectively.

A control section 320 arranged in the estimation unit 316 for estimatingat least one of the deterioration level and the discharge capabilityreceives the measured current value and the measured voltage value fromthe current sensor 314 and the voltage sensor 315, respectively, andestimates the deterioration level or the discharge capability of thebattery 312 by using the method for estimating the deterioration levelor the discharge capability according to the present invention.

In order to estimate the deterioration level or the discharge capabilityof the battery 312, the power supply system 311 of this embodiment shownin FIG. 15 is configured such that the battery 312 is discharged orcharged with a pulse current. More specifically, there is provided adischarging circuit 317 for discharging the battery 312 with the pulsecurrent. When charging the battery 312 with the pulse current, thebattery 312 can be charged by the alternator 313 through a line 318.

The method for estimating the deterioration level or the dischargecapability of the battery 312 executed by the control section 320 willbe explained in detail below by using FIG. 14. FIG. 14 is a flow chartfor explaining one embodiment of the method for estimating thedeterioration level or the discharge capability of the battery accordingto the present invention.

In the embodiment shown in FIG. 14, first, at the step S201, the currentand the voltage of the battery 312 are measured with the current sensor314 and voltage sensor 315, respectively, and the measured current valueand measured voltage value are input to the control section 320 from therespective sensor.

At the step S202, the impedance Za of the battery 312 is calculatedbased on the measured current value and the measured voltage value inputat step S201. The impedance Za can be calculated by using, for example,the Fourier expansion each of the measured current value and themeasured voltage value. Specifically, Fourier coefficients of themeasured current value and the measured voltage value are respectivelydetermined at a specified frequency and the impedance Za is calculatedfrom these two coefficients.

At the step S203, the superimposed DC component IDCa is calculated basedon the measured current value input at step S201. The DC component IDCacan be calculated by using, for example, the moving average of measuredcurrent values of a predetermined past time period from the measurementat S201. Alternatively, the DC component IDCa can be calculated by usingthe Kalman filter operation or the Fourier operation of the measuredcurrent value.

In the case of the Fourier operating of the measured current value, theconstant term in the Fourier expansion represents the DC component IDCa.More specifically, the Fourier expansion of the measured current valueis as follows:I(t)=I0+ΣIan×cos(nωt)+ΣIbn×sin(nωt)  (8)It is found from the above expression (8) that the DC component IDCa isI0 (IDCa=I0).

At the step S204, the impedance Zb at a reference direct current IDCbvalue is calculated based on both of the impedance Za calculated at thestep S202 and the DC component IDCa calculated at the step S203.Generally, since an impedance of a battery depends on the magnitude ofDC of the battery, in this embodiment the impedance Zb at the referencedirect current IDCb value is calculated from the impedance Za and the DCcomponent IDCa at the time of measurement.

One example of the impedance Za of the battery 312 varying depending onthe DC component IDCa is shown in FIG. 16 and FIG. 17. FIG. 16 and FIG.17 show the impedance Za obtained from the Fourier expansion each of themeasured current value and measured voltage value. Specifically, Fouriercoefficients of the measured current value and the measured voltagevalue are respectively determined at 2 Hz frequency and the impedance Zais calculated from these two coefficients. A real part Z′ of theimpedance Za obtained as described above is shown in FIG. 16 and animaginary part Z″ of the impedance Za is shown in FIG. 17.

According to FIG. 16 and FIG. 17, it is recognizable that the impedanceZa of the battery 312 varies greatly depending on the DC component IDCa.Especially, it is recognizable that both real and imaginary parts of theimpedance vary greatly at the low DC component range. The relationalexpression between the direct current IDC and the impedance Z describedabove can be decided in a manner so as to agree with the variation ofthe impedance with respect to the DC component shown in FIG. 16 and FIG.17.

As described above, in order to obtain the impedance Zb at the referencedirect current IDCb value based on the impedance Za and the DC componentIDCa at the time of measurement, the relational expression between thesuperimposed direct current IDC and the impedance Z is required. Therelational expression is preferably constructed to have at least oneexponential term of the superimposed direct current IDC, for example, asshown by the expression (7).

In the present embodiment, the relational expression (7) is used at thestep S204. The values of the coefficients a1, a2 . . . , b1, b2, . . .in the expression (7) are decided so that, when substituting the DCcomponent IDCa value calculated at the step S203 into the direct currentIDC of the relational expression, the impedance Z of the left sideagrees with the impedance Za calculated at the step S202.

After the coefficients being decided as described above, the impedanceZb corresponding to the reference direct current IDCb value can becalculated by substituting the reference direct current IDCb value intothe expression (7) using the coefficients thus obtained.

At the step S205, the deterioration level or the discharge capability ofthe battery 312 is determined by comparing the impedance Zbcorresponding to the reference direct current IDCb value calculated atthe step S204 with the specified impedance allowable value (hereinafterreferred as “Zth”). In other words, if the impedance Zb is judged asbeing equal to or less than the allowable value Zth, the battery 312 isdetermined as being that the deterioration level thereof is low or asbeing that the discharge capability thereof is sufficiently high (stepS206).

On the other hand, at the step S205, if the impedance Zb is judged asexceeding the impedance allowable value Zth, the battery 312 isdetermined as being that the deterioration level thereof is high or asbeing that the discharge capability thereof is insufficient (S207). Inthis case, an alarm such as “Exchange of Battery” may be displayed.

According to the present embodiment as described above, the impedance Zbat the reference direct current IDCb value is calculated from theimpedance Za and the DC component IDCa at the time of measurement andthe impedance Zb at a reference direct current IDCb value is comparedwith the specified impedance allowable value, thus the deteriorationlevel or the discharge capability of the battery 312 can be determinedat the same condition of the fixed DC value. As a result, it becomespossible to accurately determine the deterioration level or thedischarge capability of the battery 312.

Besides, since the relational expression between the superimposed directcurrent IDC and the impedance Z, which is required for obtaining theimpedance Zb at the reference direct current IDCb value based on theimpedance Za and the DC component IDCa at the time of measurement,includes at least one exponential term of the direct current IDC, forexample as the expression (7), it is possible to determine thedeterioration level or the discharge capability of the battery 312 withhigh accuracy.

In the above embodiment, the relational expression (7) is used as therelational expression between the superimposed direct current IDC andthe impedance Z, and the values of the coefficients a1, a2, . . . , b1,b2, . . . are decided in such a manner that the DC component IDCa andthe impedance Za at the time of measurement satisfy the expression (7).Alternatively, the values of each coefficient can be given by thefunctions f1(c), f2(c), . . . , g1(c), g2(c), . . . of the adjustmentparameter C so as to be able to uniquely decide the coefficients fromthe DC component IDCa and the impedance Za.

In the case where the coefficients a1, a2, . . . , b1, b2, . . . of therelational expression (7) between the superimposed direct current IDCand the impedance Z are given by the functions f1(c), f2(c), . . . ,g1(c), g2(c), . . . of the adjustment parameter C, the adjustmentparameter c is decided in such a manner that the expression (7) satisfythe DC component IDCa and the impedance Za.

Further, the functions f1(c), f2(c), . . . , g1(c), g2(c), . . . of theadjustment parameter C can be made as a linear function of C,respectively. In this case, the adjustment parameter C may beanalytically calculated from the DC component IDCa and the impedance Za.

The description of the present embodiment shows one example of a methodfor estimating a deterioration level or discharge capability of abattery according to the present invention, and the present invention isnot limited to the embodiment. Detail configuration, detail operation,and the like of the method for estimating a deterioration level ordischarge capability of a battery according to the embodiment may bemodified as needed within the sprit and scope of the present invention.

This description is based on Japanese Patent Application No. 2005-270917filed on Sep. 16, 2005 and Japanese Patent Application No. 2005-300333filed on Oct. 14, 2005, and Japanese Patent Application No. 2006-007980filed on Jan. 16, 2006. The entire contents thereof are incorporatedherein.

1. A method for detecting a state of charge (SOC) and a state of health(SOH) of a storage battery, comprising: calculating an SOC value of thestorage battery with use of an SOC calculation unit based on a measuredvoltage value or a measured current value of the storage battery, andcalculating an SOH value of the storage battery with use of an SOHcalculation unit based on the SOC value; further calculating a new SOCvalue with use of the SOC calculation unit based on the SOH value andcalculating a new SOH value with use of the SOH calculation unit basedon the new SOC value, these further calculations of SOC value and SOHvalue being repeated a prescribed n times of at least one so as toobtain an n^(th) calculated SOC value and an n^(th) calculated SOHvalue; outputting the n^(th) calculated SOH value as an SOH output valueand outputting the n^(th) calculated SOC value as an SOC output value;and storing the SOH output value into a memory.
 2. The method of claim1, wherein the SOC output value is stored in the memory.
 3. The methodof claim 1 or claim 2, wherein the SOC calculation is repeated until thenew SOH value converges to a specified range.
 4. The method of claim 1any one of claims 1, wherein a first calculated SOC value firstlyobtained with use of the SOC calculation unit is obtained by correctingthe measured voltage value or the measured current value based on eitherone of an initial SOH value set in advance and a previous SOH outputvalue lastly stored in the memory.
 5. The method of claim 1, wherein theSOH calculation unit calculates the SOH value by correcting a measuredinternal impedance value of the storage battery based on the Soc value.6. The method of claim 5, wherein the measured internal impedance valueat a measurement temperature of the storage battery is corrected to ainternal impedance value at a specified temperature.
 7. The method ofclaim 1, wherein the SOC calculation unit calculates the SOC value bysubstituting a corrected value obtained by correcting the measured valueof the OCV based on an initial SOH value or a newest SOH value into afunctional expression.
 8. The method of claim 1, wherein the SOCcalculation unit calculates a change in the SOC value based on adischarge current or a charge current of the storage battery, correctsthe change in the SOC value in accordance with SOH value, and adds thecorrected change in the SOC value to the SOC value obtained in theprevious calculation so as to calculate the new SOC value.
 9. The methodof claim 1, wherein, when the SOH output values in the memory threetimes or more are stored, a slope of the change of the SOH output valueswith respect to a number of the storing is determined, and if the laststored SOH output value falls within an allowable range, the last storedSOH output value stored in the memory is decided as a true value, whileif the last stored SOH output value is out of the allowable range, thelast stored SOH output value is deleted from the memory, and then, a newSOC output value and a new SOH output value are determined through themeasurement and/or calculation.
 10. The method of claim 1, wherein, whenthe SOH output values in the memory three times or more are stored, aslope of the change of the SOH output values with respect to a number ofthe storing is determined, and if the last stored SOH output value isout of the allowable range, an alert is issued.
 11. An apparatus fordetecting SOC and SOH of a storage battery comprising: an SOCcalculation unit configured to execute a first calculation of an SOCvalue of the storage battery based on a measured voltage value or ameasured current value of the storage battery, execute a secondcalculation of an SOC value by correcting the measured voltage value orthe measured current value of the storage battery in accordance with anSOH value of the storage battery, repeat the second calculation aprescribed n times of at least two, and output an n^(th) calculated SOCvalue as an SOC output value; an SOH calculation unit configured torepeatedly calculate an SOH value of the storage battery based on thecalculated SOC value the prescribed n times corresponding to a repeatnumber of the SOC calculation and output an nth calculated SOH value asan SOH output value; and a memory for storing at least a plurality ofthe SOH output values among the SOH and SOC output values, respectivelyobtained in the n^(th) calculation.
 12. The apparatus of claim 11,further comprising: a control unit configured to determine a slope of achange of the SOH output values with respect to a number of the storingtimes in the memory when the SOH output value is stored in the memorythree times or more, decide a newest SOH output value as a true value ifthe newest stored SOH output value of the stored values falls within anallowable range, and delete the newest SOH output value and obtain againan SOC output value and an SOH output value through the measurementand/or the calculation if the newest SOH output value is out of theallowable range.